JP3122494B2 - Manufacturing method of pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a pressure sensor.

[0002]

2. Description of the Related Art As a pressure sensor, for example, a pressure detecting element such as a diffusion resistance element or a capacitance element is provided on one side of a silicon wafer, and a diaphragm is provided from the other side of the silicon wafer so as to correspond to the pressure detecting element. Is formed by etching.

In the case of manufacturing a pressure sensor of this type, since the pressure sensing element is formed using one flat surface of a silicon wafer, the diaphragm must be formed from the other side. Therefore, it is necessary to match the patterns on both surfaces of the silicon wafer with each other, but since it is not possible to use a mask aligner used in general thin film technology and semiconductor processes, conventionally, using a double-sided mask aligner, The pattern was being matched.

[0004]

However, the double-sided mask aligner is a very special mask aligner, which is used only for manufacturing a pressure sensor, and is extremely expensive. Therefore, the conventional pressure sensor must be manufactured using a special mask aligner, which inevitably increases the cost.

The present invention has been made in consideration of the above-mentioned matters, and has as its object to eliminate the necessity of using special and expensive equipment such as a double-sided mask aligner. It is an object of the present invention to provide a method which can be used and can manufacture a pressure sensor simply and at low cost.

[0006]

To achieve the above object, according to an aspect of, the present invention, the pressure sensing element provided on one side of the single silicon wafer, so as to correspond to the pressure sensing element, the other silicon wafer In a method for manufacturing a pressure sensor, wherein a diaphragm is formed by etching from the side, before forming the diaphragm, at least two through holes for mask alignment are provided in the silicon wafer, and the side of the through hole is formed of silicon. Crystal
It is in line with the rank .

[0007]

In the method of the present invention, the through holes formed in the silicon wafer can be used as a mask alignment pattern, so that the patterns on both sides of the silicon wafer can be easily adjusted.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an example of a method for manufacturing a pressure sensor according to the present invention. As shown in FIG. 1A, etching masks 2 and 3 such as a silicon nitride film (SiN) are formed on both upper and lower surfaces of a silicon wafer (hereinafter, referred to as a wafer) 1.

Next, by using phosphoric acid, hydrofluoric acid, or the like as an etchant, a predetermined portion of the etching mask 3 on the lower side of the wafer 1 is dissolved to form two through-hole etching patterns (for example, squares) 4 for example. (See FIG. 1B).

Then, using an alkaline aqueous solution such as KOH as an etchant, the wafer 1 is anisotropically etched to form a square through hole 5 of a predetermined size for mask alignment (see FIG. 1C). ). In this case, if the plane of the wafer 1 is the (100) plane, the angle α in FIG. 1C becomes 55 °, and the inclined through hole 5 is formed.
If the plane of the wafer 1 is the (111) plane, the angle α is 90 °, and etching is performed vertically.

When the through-hole 5 is square as in this embodiment, as shown in FIG. 3, the sides thereof are along the orientation of the silicon crystal, which is convenient. In the following steps, the through holes 5 are used as an alignment pattern. In FIG. 3, 6 is a sensor chip, and 7 is an orientation flat.

After the through holes 5 are formed in the wafer 1 as described above, first, a predetermined portion of the etching mask 3 on the lower side of the wafer 1 is dissolved using phosphoric acid to form a diaphragm etching pattern 8. Is formed (see FIG. 2A). In this case, the lower opening 5d of the through hole 5 is used as an alignment pattern.

Then, the wafer 1 is anisotropically etched using KOH to form a diaphragm 9 on the lower portion of the wafer 1 (see FIG. 2B).

Next, the etching masks 2 and 3 on both surfaces of the wafer 1 are removed using phosphoric acid (see FIG. 2C).

The pressure detecting element 10 is provided above the wafer 1.
To form a diffusion resistance. In this case, the upper opening 5u of the through hole 5 is used as an alignment pattern. Then, a bonding pad is formed on the upper surface of the wafer 1 and an electrode 11 is formed (see FIG. 2D). It is preferable to finish the diaphragm 9 by immersing it in an alkaline aqueous solution such as KOH.

Further, the glass substrate 12 is bonded to the lower surface of the wafer 1 to perform anodic bonding, thereby forming a sealed chamber 13 surrounded by the silicon wafer 1, the diaphragm 9 and the glass substrate 12, and dicing and wire bonding. By performing the bonding, a pressure sensor 14 as shown in FIG. 2E is obtained.

As will be understood from the above description of the manufacturing flow, in the method of manufacturing the pressure sensor according to the present invention, the through-hole 5 formed in the wafer 1 is used as a mask alignment pattern. The patterns on both sides can be easily matched. Therefore, unlike the related art, the pressure sensor 14 can be easily manufactured without using special and expensive equipment such as a double-sided mask aligner.

In the above manufacturing flow, anisotropic etching is performed twice. However, when a high-concentration boron diffusion layer or an epitaxial layer is used as an etch stop layer for the diaphragm 9, the formation of the diaphragm 9 and the formation of a through hole are performed. 5 can be formed at the same time, which is simpler than the above production flow.

The method of manufacturing the pressure sensor according to the present invention is not limited to the above embodiment. For example, the etching masks 2 and 3 may be formed of an oxide film. In this case, it is preferable to use hydrofluoric acid as the etchant. Then, instead of the diffusion resistor 10, an electrode for measuring capacitance may be formed. Further, two through holes 5 for mask alignment are formed.
More than one may be provided. Further, the shape of the through-hole 5 may be a square such as a rectangle in addition to the above-mentioned square.

The pressure sensor 14 shown in FIG.
Was used for absolute pressure measurement, but as shown by phantom lines in this figure, a hole 15 was provided in the glass substrate 12,
A structure for measuring the gauge pressure such that both sides of the diaphragm 9 are to be measured may be employed.

[0022]

As described above, according to the present invention,
Unlike the related art, there is no need to use special and expensive equipment such as a double-sided mask aligner, and the pressure sensor can be easily and inexpensively manufactured using ordinary thin film forming equipment.

[Brief description of the drawings]

1 (A) to 1 (C) show an example of a method for manufacturing a pressure sensor according to the present invention, and particularly, from a step of forming an etching mask on a silicon wafer to forming a through hole for mask alignment. It is a figure which shows the process until it does.

2 (A) to 2 (E) show a continuation of the method of manufacturing the pressure sensor, wherein a pressure sensor is obtained by forming a diaphragm and a pressure detecting element from a step of forming a diaphragm etching pattern on a silicon wafer. FIG.

FIG. 3 is a plan view showing a state in which a through hole is formed in a silicon wafer.

[Explanation of symbols]

1: silicon wafer, 5: through hole, 9: diaphragm,
10… Pressure detection element, 14… Pressure sensor.

Claims (1)

(57) [Claims] 1. A pressure sensing element provided on one side of the single silicon wafer, so as to correspond to the pressure sensing element,
In a method of manufacturing a pressure sensor, wherein a diaphragm is formed by etching from the other side of a silicon wafer, at least two through holes for mask alignment are provided in the silicon wafer before the formation of the diaphragm . Side is along the direction of the silicon crystal
The manufacturing method of the pressure sensor characterized by doing so .